Hey everyone, intresting problem here in my 85, 5.0 L 302, f 150. My tail lights are working, but my brake lights are not, my one and only working turn signal is my rear driver side (no front turn signals either), and my reverse lights are non existent, at first the only side I could get to flash was my rear passenger side, but it was the fast blink as if the front was burned out, and it only worked when I was using my hazard lights... I changed the fuses with ones from my old wiring harness and suddenly it switched sides... Weird right? When I engage my turn signals the lights on the dash are constantly lit, no flashing, when I use the hazard lights, they flash normally (dash lights). I know the wiring is right, because I checked everything out with my Haynes wiring diagrams when I installed it, I'm down to a possible bad ground or grounds, or all my switches are bad, which sounds unlikely but could be very well possible considering the previous owner.... Weigh in with your thoughts, I'm really not sure how to assess this problem, and it's the last thing I need to fix to have it on the road! Thanks everyone!

 

have you checked your turn signal switch the one on my 81 f100 is worn out and i find i have to jiggle the the arm to get the brake lights to work

 

The brake/turn signal lamps are their own circuit; yes, investigate your turn signal switch.

Parking/running lamps are a different, independent circuit; backup lamps are yet another circuit. Sounds like you have multiple problems....

 

That's kind of what I thought, but I'm actually surprised the brake lights and turn signals are a circuit, I'll check on it and let you guys know!

 

Actually now that I'm thinking about it I'm not surprised they are one circuit, I guess it'd have to be one to flash when you hit the brakes!

 

New switch didn't work... In fact now the left turn signal only flashes when the hazard lights are on....

 

Well, if the behavior changed after changing the switch, there is something about that old switch.

The lights coming and staying on in the dash say a lot - some circuit isn't being completed correctly and electricity is following the path of least resistance (which happens to be through the dash in this case). I have seen others here talk about it (81-F-150-Explorer, maybe @Franklin2 I don't remember exactly who for certain).

What I would suggest doing is :

1) Check all of your multi-circuit bulbs - the ones with two filaments in them - two in the front, two in the back... Weird things can happen when one of those filaments inside the bulb breaks and falls down and crosses onto the other filament.

2) Verify and clean all your grounds related to the exterior lighting.

3) Poorly installed, user-added trailer wiring kits are a common cause of this kind of grief....

 

Ok figured out the front turn signals and in turn fixed the back left, when I checked the bulbs I noticed there was the peanut butter like stuff in the sockets, I cleaned most of it out put the bulbs back in and now the fronts are working fine, the only one not working is my rear passenger side now....

 

Now what's happening is the left turn signals are working fine, blinking correctly and everything, the right turn signal is just staying lit no blinking no fast blinking signaling its dead, just staying lit, based upon the behavior of the left side, I would assume that signifies an open circuit to the rear turn signal, which is odd because the driving light back there works fine....

 

Sounds like a bad ground - run a temporary long ground wire from the neg. battery terminal back to the taillight housing, make sure that you have a good connection and retest. If it works, install a short ground wire from the housing to the body then to the frame.

 

I actually just figured it out! I guess a got a bad bulb, tried the extra one I ordered and it worked perfectly! Gotta love 5 cent bulbs from rock auto lol I'll get a helper and check the brake lights!

 

The running lamp/parking lamp/driving light is an entirely separate circuit from the turn signals/brake lights - it uses the brown wire which runs all throughout the truck and powers:

- front/rear parking lamps
- roof-mounted clearance lamps (if equipped)
- rear license plate illumination
- front side marker lamps

There are several grounds for all of the above, distributed throughout the truck.

Just FYI.

 

Oh! Thanks, Ctubutis! Idk how you know all this stuff but it's impressive really! Haha so turn signals are all accounted for, now the brake lights, not getting anything as far as brake lights... Should I start at the brake switch?

 

You can start at the brake light switch if you like. Test for power... one of the leads should have power all of the time; they should both have power when the switch is closed, i.e. you have the brakes on.

From there, power is manipulated in the turn signal switch....@Franklin2 knows offhand more of the specifics from there, I need to look in the books so hopefully he'll chime in if needed.

How do I know all of this stuff? Well, I've been interested in computers & electronics (and electricity by extension) and cars since I was a pre-teen, I used to watch my father and his friends build Stock Cars in our garage. And I started dorkin' around with stuff when I got my first car in high school, a 1970 Mustang fastback with a 351Wheezer and FMX automatic.

Fast forward 36 years to today, and I have the factory shop manuals & wiring diagrams for my own 1981 truck as well as a handful of 80s & 90s cars and my brother's Bronco - all of which I have done extensive work on, some of which are still on the road.

So, in the end, I guess the answer was best given by Ferris Bueller: Years of practice.

 

Hi,

i just replace the hole wirings for any lights on my 1985 F350 Rachecarhauler, so i think i am in the position to help a Little.

The Lights on the rear (parking/Drive) are powert with the brown Cable comes from Ligthswitch

The Turnsignal comes from the Switch behind the Steeringweel Colours are:

- LH Front= Lightgreen/White
- RH Front= Withe/Blue
- LH Rear = Lightgreen/orange
- RH Rear = Orange/lightblue

- Brakelight Power is Lightgreen/red Hash
- Brakelightwirig to Turnsignalswitch and Cruisecontrol is green

You find all Wirings for testing in the halfround Connector under the Steering column.

The Hazardswitch overwright all Turnsignal and Brakeswitchsignals

For me i think you have a bad Turnsignalswitch.

The Backuplamps switch at manual transmission is on the Gearbox driverside, Wiring is:

Power from Fusebox Fuse 5 to Turnsignalflasher from there wiring Pink/Orange Hash to Backup switch, from Switch to lamps Black/Pink

Best regards

Torsten from Germany